One field where high pressure couplings are regularly required is in the field of spray washing systems in which high pressure fluid for high pressure spray nozzles is communicated from a stationary supply line to a rotary member. In some cases the rotary member carries a plurality of high pressure nozzles which are rotated around an axis to effect a washing action. In other cases, the rotary member is simply pulled from place to place so that it is necessary for rotation to occur around a mounting member so that for example a hand held wand can be moved to a number of different locations from a central stationary supply.
While the present invention is describe(d particularly in relation to washing systems of this type, the coupling described and claimed herein is not limited to such end uses.
One example of a rotary coupling for supplying fluid from a stationary supply to a rotatable boom is shown in U.S. Pat. No. 4,998,693 of the present inventor issued Mar. 12, 1991 wherein FIG. 5 there is shown a stationary axle having a high pressure water supply to one end of the axle. A first mechanical bearing supports the boom and hose for rotation about the axle. A second fluid coupling on one end of the mechanical bearing allows the supply of the high pressure fluid from the axle to a pipe which rotates around the axle. The second fluid coupling transfers fluid only and carries no loads.
This design has achieved some success when the fluid transfer swivel is not subjected to carrying a load, but is limited in the ability to properly supply the high pressure fluid to the hose. Particularly, the design has not adequately separated the fluid transfer and weight carrying components resulting in poor wear characteristics.
In most washing systems of the above general type, a rotating axle carries on one end a wand having a plurality of nozzles. The axle is driven by a pulley on an opposite end of the axle from the wand. The axle is mounted for rotation simply in the rotary high pressure coupling which therefore simultaneously provides both the mechanical support and the sealing relative to the axle of the high pressure fluid supply. This design has the advantage that it is relatively simple but is prone to early failure due to the fact that the mechanical forces from the pulley and the wand are applied in a radial direction to the seals thus leading to premature failure of the seals and early replacement.
It is one object of the present invention, therefore, to provide an improved rotary coupling for high pressure fluid which displays increased longevity and improved mechanical stability by separating the fluid transfer and the weight carrying components.